Drip line starts then stops
I'm at a loss. I have a drip system with two zones on an automatic timer. The front yard (zone two) works fine, good pressure,etc. and it's been running about two years. The backyard line(zone one) was capped off and never used. I've now run a drip line through the backyard and attached it to the zone one line. Before I did too much landscaping I put in 7 plants to test the system. When I turned the system on for manual watering it came on and I thought 'Success!' and set it for scheduled auto watering like the front yard. I travel so about 2 weeks went by and I came home to dry,half-dead plants. I've been watching the system. When zone one time begins the water starts dripping...then peters out and stops after 2-3 minutes. When timer finishes counting down and switches to zone one everything returns to normal. Front yard gets full watering time and good pressure. Anyone have any ideas what's going on?